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Apex 1 - 2 Respiratory II: Physiology (24) > West Zones > Flashcards

Flashcards in West Zones Deck (44)
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1

In each alveolar unit, the ventilation to perfusion ratio is determined by the relative pressures between which four variables?

  1. Alveolus
  2. Arterial capillary
  3. Venous capillary
  4. Interstitial space

2

Originally, what was believed to be the most significant influence on the distribution of perfusion throughout the lung?

Gravity

3

Originally, gravity was believed to be the most significant influence on the distribution of perfusion throughout the lung. This hypothesis stated that:

A. the base received more blood flow than the apex.

B. the apex received more blood flow than the base.

A. the base received more blood flow than the apex.

4

Originally, gravity was believed to be the most significant influence on the distribution of perfusion throughout the lung. This hypothesis stated that the base received more blood flow than the apex.

Today, we understand that the blood flow follows more of a ---------    distribution.

Central to peripheral

5

Today, we understand that the blood flow follows more of a central to peripheral distribution, where zone Ill is found at the

Lower central core

6

Today, we understand that the blood flow follows more of a central to peripheral distribution, where zone Ill is found at the lower central core and zone II and zone I

radiate towards the periphery

(as concentric spheres)

7

Classic explanation of lung zones is essential to understanding this topic.

Which west Zone correspond to Dead Space?

Zone I = Dead Space

8

What's the relationship between PA, Pa, and Pv in Zone I?

PA> Pa >Pv

9

In Zine I, what's the value of V/Q?

V/Q = ∞

There is ventilation, but there is no perfusion

10

True or False:

Zone I usually does not occur in normal lung

True

Zone I usually does not occur in normal lung

11

How do hypotension, pulmonary embolus, or excessive airway pressure affect Zone I?

Zone I is increased

12

What do the bronchioles of un-perfused alveoli do to combat zone I?

Constrict to reduce dead space

13

Which west Zone correspond to Waterfall?

Zone II = Waterfall

14

What's the relationship between PA, Pa, and Pv?

Zone II: Pa > PA > Pv

15

What's the value of V/Q in Zone II?

V/Q = 1

(There is ventilation and perfusion)

16

Why is Zone II referred to as Waterfall?

Think of a waterfall flowing over a dam, where Pa is the height of the upstream river and PA is the height of the dam. A greater height of the upstream river translates into a higher rate of water flow over the dam

17

In Zone II, Like our waterfall analogy, blood flow is directly proportional to the difference between:

Pa - PA

18

In Zone II, Like our waterfall analogy, blood flow is directly proportional to the difference between Pa - PA. The greater the difference between Pa - PA, the greater the

Blood flow

19

It is possible for a zone II unit to transiently change to zone I or zone Ill. Why is this possible?

Changes in Pulmonary capillary pressure and Alveolar pressure change throughout the respiratory cycle

In other words, if is PA>Pa>Pv, Zone II will transiently change to Zone I

If Pa>Pv>PA, Zone II will transiently change to Zone III

20

Which west Zone correspond to Shunt?

Zone Ill = Shunt

21

What's the relationship between Pa, PA, and Pv in Zone III?

Zone III: Pa > Pv > PA

22

In Zone III, Blood flow is a function of:

Pulmonary arteriovenous pressure difference

(Pa - Pv)

23

In the absolute sense, when there is blood flow in the absence of ventilation, what occurs?

Shunt

24

What's the value of in Zone III or shunt?

V/Q = 0

25

Most zone III units are "shunt- like" - What does that mean?

They are better perfused than they are ventilated (V< Q).

26

To combat zone III,    ------    reduces pulmonary blood flow to under-ventilated units.

Hypoxic Pulmonary Vasoconstriction  (HPV)

27

In Zone III, since the pressure in the capillary is always higher than the alveolus, the vessel is always open, and blood is always moving through it. True or False

True

28

Why should the tip of the pulmonary artery catheter be placed in zone III?

Blood is always moving through Zone III

(Since the pressure in the capillary is always higher than the alveolus, the vessel is always open)

29

True or False:

All Shunt Occurs in the Lungs

False

Not All Shunt Occurs in the Lungs

30

Any venous blood that empties directly into the left side of the heart is described as:

Anatomic shunt